Towards more thermally stable Li-ion battery electrolytes with salts and solvents sharing nitrile functionality
Journal article, 2016

The overall safety of Li-ion batteries is compromised by the state-of-the-art electrolytes; the thermally unstable lithium salt, lithium hexafluorophosphate (LiPF6), and flammable carbonate solvent mixtures. The problem is best addressed by new electrolyte compositions with thermally robust salts in low flammability solvents. In this work we introduce electrolytes with either of two lithium nitrile salts, lithium 4,5-dicyano-1,2,3-triazolate (LiDCTA) or lithium 4,5-dicyano-2-trifluoromethylimidazolide (LiTDI), in solvent mixtures with high flashpoint adiponitrile (ADN), as the main component. With sulfolane (SL) and ethylene carbonate (EC) as co-solvents the liquid temperature range of the electrolytes are extended to lower temperatures without lowering the flashpoint, but at the expense of high viscosities and moderate ionic conductivities. The anodic stabilities of the electrolytes are sufficient for LiFePO4 cathodes and can be charged/discharged for 20 cycles in Li/LiFePO4 cells with coulombic efficiencies exceeding 99% at best. The excellent thermal stabilities of the electrolytes with the solvent combination ADN:SL are promising for future electrochemical investigations at elevated temperatures (> 60 degrees C) to compensate the moderate transport properties and rate capability. The electrolytes with EC as a co-solvent, however, release CO2 by decomposition of EC in presence of a lithium salt, which potentially makes EC unsuitable for any application targeting higher operating temperatures.

LiDCTA

Li-ion battery

Sulfolane

LiTDI

High flashpoint electrolytes

Adiponitrile

Author

Manfred Kerner

Chalmers, Physics, Condensed Matter Physics

Du Hyun Lim

Chalmers, Physics, Condensed Matter Physics

Steffen Jeschke

Chalmers, Physics, Condensed Matter Physics

Tomas Rydholm

Chalmers, Signals and Systems, Signalbehandling och medicinsk teknik, Biomedical Electromagnetics

J. H. Ahn

Gyeongsang National University

Johan Scheers

Chalmers, Physics, Condensed Matter Physics

Journal of Power Sources

0378-7753 (ISSN)

Vol. 332 204-212

Subject Categories

Materials Chemistry

DOI

10.1016/j.jpowsour.2016.09.101

More information

Created

10/8/2017